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From: Vineet Gupta <Vineet.Gupta1@synopsys.com>
To: linux-snps-arc@lists.infradead.org
Cc: Peter Zijlstra <peterz@infradead.org>,
	Will Deacon <will@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
	Mark Rutland <mark.rutland@arm.com>,
	linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
	Vladimir Isaev <Vladimir.Isaev@synopsys.com>,
	Vineet Gupta <Vineet.Gupta1@synopsys.com>
Subject: [PATCH 02/11] ARC: atomic: !LLSC: remove hack in atomic_set() for for UP
Date: Wed,  4 Aug 2021 12:15:45 -0700	[thread overview]
Message-ID: <20210804191554.1252776-3-vgupta@synopsys.com> (raw)
In-Reply-To: <20210804191554.1252776-1-vgupta@synopsys.com>

!LLSC atomics use spinlock (SMP) or irq-disable (UP) to implement
criticla regions. UP atomic_set() however was "cheating" by not doing
any of that so and still being functional.

Remove this anomaly (primarily as cleanup for future code improvements)
given that this config is not worth hassle of special case code.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
---
 arch/arc/include/asm/atomic-spinlock.h | 17 ++++-------------
 1 file changed, 4 insertions(+), 13 deletions(-)

diff --git a/arch/arc/include/asm/atomic-spinlock.h b/arch/arc/include/asm/atomic-spinlock.h
index bdf87610b2d7..8c6fd0e651e5 100644
--- a/arch/arc/include/asm/atomic-spinlock.h
+++ b/arch/arc/include/asm/atomic-spinlock.h
@@ -3,12 +3,10 @@
 #ifndef _ASM_ARC_ATOMIC_SPLOCK_H
 #define _ASM_ARC_ATOMIC_SPLOCK_H
 
-#ifndef CONFIG_SMP
-
- /* violating atomic_xxx API locking protocol in UP for optimization sake */
-#define arch_atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))
-
-#else
+/*
+ * Non hardware assisted Atomic-R-M-W
+ * Locking would change to irq-disabling only (UP) and spinlocks (SMP)
+ */
 
 static inline void arch_atomic_set(atomic_t *v, int i)
 {
@@ -30,13 +28,6 @@ static inline void arch_atomic_set(atomic_t *v, int i)
 
 #define arch_atomic_set_release(v, i)	arch_atomic_set((v), (i))
 
-#endif
-
-/*
- * Non hardware assisted Atomic-R-M-W
- * Locking would change to irq-disabling only (UP) and spinlocks (SMP)
- */
-
 #define ATOMIC_OP(op, c_op, asm_op)					\
 static inline void arch_atomic_##op(int i, atomic_t *v)			\
 {									\
-- 
2.25.1


WARNING: multiple messages have this Message-ID (diff)
From: Vineet Gupta <Vineet.Gupta1@synopsys.com>
To: linux-snps-arc@lists.infradead.org
Cc: Peter Zijlstra <peterz@infradead.org>,
	Will Deacon <will@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
	Mark Rutland <mark.rutland@arm.com>,
	linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
	Vladimir Isaev <Vladimir.Isaev@synopsys.com>,
	Vineet Gupta <Vineet.Gupta1@synopsys.com>
Subject: [PATCH 02/11] ARC: atomic: !LLSC: remove hack in atomic_set() for for UP
Date: Wed,  4 Aug 2021 12:15:45 -0700	[thread overview]
Message-ID: <20210804191554.1252776-3-vgupta@synopsys.com> (raw)
In-Reply-To: <20210804191554.1252776-1-vgupta@synopsys.com>

!LLSC atomics use spinlock (SMP) or irq-disable (UP) to implement
criticla regions. UP atomic_set() however was "cheating" by not doing
any of that so and still being functional.

Remove this anomaly (primarily as cleanup for future code improvements)
given that this config is not worth hassle of special case code.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
---
 arch/arc/include/asm/atomic-spinlock.h | 17 ++++-------------
 1 file changed, 4 insertions(+), 13 deletions(-)

diff --git a/arch/arc/include/asm/atomic-spinlock.h b/arch/arc/include/asm/atomic-spinlock.h
index bdf87610b2d7..8c6fd0e651e5 100644
--- a/arch/arc/include/asm/atomic-spinlock.h
+++ b/arch/arc/include/asm/atomic-spinlock.h
@@ -3,12 +3,10 @@
 #ifndef _ASM_ARC_ATOMIC_SPLOCK_H
 #define _ASM_ARC_ATOMIC_SPLOCK_H
 
-#ifndef CONFIG_SMP
-
- /* violating atomic_xxx API locking protocol in UP for optimization sake */
-#define arch_atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))
-
-#else
+/*
+ * Non hardware assisted Atomic-R-M-W
+ * Locking would change to irq-disabling only (UP) and spinlocks (SMP)
+ */
 
 static inline void arch_atomic_set(atomic_t *v, int i)
 {
@@ -30,13 +28,6 @@ static inline void arch_atomic_set(atomic_t *v, int i)
 
 #define arch_atomic_set_release(v, i)	arch_atomic_set((v), (i))
 
-#endif
-
-/*
- * Non hardware assisted Atomic-R-M-W
- * Locking would change to irq-disabling only (UP) and spinlocks (SMP)
- */
-
 #define ATOMIC_OP(op, c_op, asm_op)					\
 static inline void arch_atomic_##op(int i, atomic_t *v)			\
 {									\
-- 
2.25.1


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  parent reply	other threads:[~2021-08-04 19:16 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-04 19:15 [PATCH 00/11] ARC atomics update Vineet Gupta
2021-08-04 19:15 ` Vineet Gupta
2021-08-04 19:15 ` [PATCH 01/11] ARC: atomics: disintegrate header Vineet Gupta
2021-08-04 19:15   ` Vineet Gupta
2021-08-04 19:15 ` Vineet Gupta [this message]
2021-08-04 19:15   ` [PATCH 02/11] ARC: atomic: !LLSC: remove hack in atomic_set() for for UP Vineet Gupta
2021-08-04 19:15 ` [PATCH 03/11] ARC: atomic: !LLSC: use int data type consistently Vineet Gupta
2021-08-04 19:15   ` Vineet Gupta
2021-08-04 19:15 ` [PATCH 04/11] ARC: atomic64: LLSC: elide unused atomic_{and,or,xor,andnot}_return Vineet Gupta
2021-08-04 19:15   ` [PATCH 04/11] ARC: atomic64: LLSC: elide unused atomic_{and, or, xor, andnot}_return Vineet Gupta
2021-08-04 19:15 ` [PATCH 05/11] ARC: atomics: implement relaxed variants Vineet Gupta
2021-08-04 19:15   ` Vineet Gupta
2021-08-04 19:15 ` [PATCH 06/11] ARC: switch to generic bitops Vineet Gupta
2021-08-04 19:15   ` Vineet Gupta
2021-08-04 19:15 ` [PATCH 07/11] ARC: bitops: fls/ffs to take int (vs long) per asm-generic defines Vineet Gupta
2021-08-04 19:15   ` Vineet Gupta
2021-08-04 19:15 ` [PATCH 08/11] ARC: xchg: !LLSC: remove UP micro-optimization/hack Vineet Gupta
2021-08-04 19:15   ` Vineet Gupta
2021-08-04 19:15 ` [PATCH 09/11] ARC: cmpxchg/xchg: rewrite as macros to make type safe Vineet Gupta
2021-08-04 19:15   ` Vineet Gupta
2021-08-04 19:15 ` [PATCH 10/11] ARC: cmpxchg/xchg: implement relaxed variants (LLSC config only) Vineet Gupta
2021-08-04 19:15   ` Vineet Gupta
2021-08-04 19:15 ` [PATCH 11/11] ARC: atomic_cmpxchg/atomic_xchg: implement relaxed variants Vineet Gupta
2021-08-04 19:15   ` Vineet Gupta
2021-08-05  9:02 ` [PATCH 00/11] ARC atomics update Peter Zijlstra
2021-08-05  9:02   ` Peter Zijlstra
2021-08-05 16:18   ` Vineet Gupta
2021-08-05 16:18     ` Vineet Gupta
2021-08-05 17:04     ` Peter Zijlstra
2021-08-05 17:04       ` Peter Zijlstra
2021-08-05 19:14       ` [RFC] bitops/non-atomic: make @nr unsigned to avoid any DIV Vineet Gupta
2021-08-05 19:14         ` Vineet Gupta
2021-08-06 13:42         ` Will Deacon
2021-08-06 13:42           ` Will Deacon
2021-08-06 19:02           ` Vineet Gupta
2021-08-06 19:02             ` Vineet Gupta
2021-08-06  8:41       ` [PATCH 00/11] ARC atomics update Will Deacon
2021-08-06  8:41         ` Will Deacon

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